Process of silicidizing.



F. J. TONE & T. B. ALLEN.

PROCESS OF SILIGIDIZING.

APPLICATION FILED SEPT. 17, 1912.

1,054,372. PatentedFeb. 25, 1913.

WITNESSES INVENTORB a. s. Q

UNITED STA PATEN FFTQ.

FRANK J. TONE AND THOMAS B. ALLEN, OF NIAGARA FALLS, NEW YORK, ASSIGNORS TO THE CARBORUNDUM COMPANY, OF NIAGARA FALLS, NEW YORK, A CORPORA- TION OF PENNSYLVANIA.

PROCESS OF SILICIDTZIN G.

Application filed September 17, 1912.

To all whom it may concern:

Be it known that we, FRANK J. Toxr. and T HouAs B. Aiinnmboth residents of Niagara Falls, in the county of Niagara and State of New York, have invented a new and useful Process of Silicidizing, of which the following is a full, clear, and exact description, reference being bad to the accompanying drawings, forming part of this specification, in which Figure 1 is a vertical section of one form Specification of Letters ?atent.

of furnace which may be employed in carrying out our invention; and Flgs. 2, 3 and 4t are similar views illustrating other forms of furnaces.

This invention has relation to a new and useful process for the conversion of shaped articles into silicon carbid. In accordance with the process described in United States Patent 992,698, issued to Frank J. Tone. May 16th, 1911, shaped articles consisting of silicon carbid and carbonaceous material are subjected to the action of silicon-containing vapors at a suitable temperature whereby thecarbonaceous material is changed into silicon cal-bid. The resultant articles 'consist, therefore, of substantially pure silicon cal-bid and have many valuable uses for electrical and refractory purposes. It is found very diflicult to effect acomplete conversion of silicidization throughout the whole mass and particularly in the interior of the mass. \Ve have found that the depth of penetration and the concentration of the siliconcontaining vapors in the shaped articles is' dependent, among other things, on the partial pressures of these vapors; and that it is essential to have a high vapor tension of the silicon-containing vapors in order to yield products of large mass which are completely silicidized. It has been the practice to effect the silicidizing action by the use of an electrical incandescent furnace. Ve have now found that the electric arc furnace process is very efficient and economical-and that it is readily possible to obtain a high vapor pressure of the silicon'containing vapors by the use of the arc.

- e will now describe a preferred manner in which the invention may be carried out, reference being made to the accompanying drawing forming part of this specification. Fig. 1 shows a sectional elevation of a suitable type of furnace. 0 is the base of Patented Feb. 25, 1913.

Serial No. 720,766.

the furnace n ade of refractory material and 3, 3 are the side walls forming a receptacle open at the top. l, l are vertical superposed electrodes, the lower electrode extending through the baseof the furnace and the upper electrode being adjust-ably suspended in a vertical line above it. 5, 5 represent the shaped articles which may consist of a mixture of 80% by weight of silicon carbid and 20% by weight of petroleum coke, being bound with a temporary binder, such as tar or glutrin and pressed into the required shapes. 6 is a mixture which may be composed of 70 parts by weight of silica sand and 30 parts by weight of coke. In certain cases, it is desirable to have this mixture porous for the free circulation of the gases, and in such cases it is advantageous to add 10% of saw-dust; or instead of this, the mixture may be briqueted or coarsely ground. After the furnace is thus charged, the elec tric arc is started between the electrodes and the mixture of silica and carbon surrounding the arc and the charge of shaped articles to be converted is raised to the formation temperature of silicon carbid. A cavity is formed around the arc, the walls of the cavity being composed of silicon carbid. This prevents the mixture from falling into the space between theelectrodes and forming a resistance path for the current from one electrode to the other.. There is also substantially little leakage of current from the mixture around the arc zone from one electrode to the other, the major portion of the energy being expended in the arc. The process is continued at this temperature until a definite amount of electrical energy is consumed. This is found by experiment and varies with different shaped bodies. \Vhen the process is finished the furnace charge is removed and the articles are obtained converted into the desired form of silicon carbid.

Many other furnace arrangements arepossible for obtaining silicidization by means of the arc. v

In Fig. 2 we show a form in which the arc is placed directly upon the articles to be silicidized. The base 8 of the furnace constitutes one terminal of the furnace and the electrode 9 the other terminal. The block 10 to be silicidized is laid on the base of the furnace to make electrical contact therewith.

sequently the loss of electrical ener superposed electrodes extending through the base and cover of the furnace. The article to'be silicidizedis, for example a cylinder 16, consisting of silicon carbid and carbon, of the proportions already stated for the shaped articles in Fig. 1. The are is sprung between the electrodes, and silicon-containing vapors are obtained by introducing silicious material through the passage in the upper elect-rode. This material may be silica in powdered form or some volatile compound of silicon.

' In Fig. 4 is shown a method in which a closed chamber 17 is heated by means of arcs, produced by electrodes 18, and in which the silicon-containing vapors are generated in a mixture 19 of silica and carbon surrounding the arcs and the chamber are caused to permeate the chamber and silici' dizes articles which are placed therein.

The methods we have described have great advantages in that the heat can be generated just where it is desired and cony 15 very small and the process eflicient. Furthermore, the heat can be confined in a comparatively small space and it is, therefore, a

simple matter to obtain ahigh vapor pressure of the silicon-containing gases. On account of the ability toobtain a high partial pressure of the silicon-containing vapors the products obtained are much more completely silicidized and are, therefore, tougher and have many other advantages for electrical and refractory purposes.

1. The process of converting shaped carbonaceous articles into silicon carbid, which consists in subjecting said articles to the action of silicon-containing Vapors of high vapor pressure produced by the electric are.

2. The process of silicidiz'mg carbonaceous articles which consists of placing said articles in a mixture of siliceous and carbonaceous material, and forming an electric are within said mixture whereby said arti cles are heated and silicon-containing vapors are caused to permeate the articles and silicidize them.

3. The process of silicidizing carbonaw.

ceous articles, which consists in surrounding them with a material capable of producing silicon-containing vapors. and then subjecting the articles and material to heat generated by an electric arc.

in testimony whereof. we have hereul'ito set our hands. 1 FRANK J. TONE. THOS. B. ALLEN.

lVitnesses as to Frank J. Tone:

THos. DEAN, W. A. DWYER.

JOHN BAKER. 

